The present invention relates to the process control industry. More particularly, the present invention relates to a remote diaphragm assembly or seal, of the type used to couple a process control instrument to a process.
Some types of process control instruments, such as pressure transmitters, have a diaphragm seal which is fluidically coupled to a remote diaphragm assembly by a fill fluid. The remote diaphragm assembly includes a flexible diaphragm that isolates the diaphragm seal of the pressure transmitter from corrosive process fluids contained in a vessel and allows the pressure transmitter to couple to the pressure of the vessel. The fill fluid is substantially incompressible and completely fills the cavities between the flexible diaphragm and the diaphragm seal including a capillary tube (or a thru hole if the remote diaphragm assembly is directly mounted to the process control instrument). The capillary tube is typically flexible and may extend for several meters to safely separate the transmitter from the process. Pressure exerted by the process fluid on the diaphragm is transferred through the fill fluid from the flexible diaphragm to the diaphragm seal of the transmitter which relays the pressure to a sensor contained within the transmitter.
The remote diaphragm assembly often includes a diaphragm housing and an adapter housing. The adapter housing is used to interface with a process flange which is attached to the vessel and provides access to the process fluid contained therein. The diaphragm housing mates to the adapter housing and includes a thin flexible diaphragm which, on one side is placed in fluid communication with the process fluid and, on the other side, is placed in fluid communication with the fill fluid. The remote diaphragm assembly may also include a gasket sandwiched between the diaphragm housing and the adapter housing to provide leakage protection. Another gasket is generally positioned between the adapter housing and the process flange to provide leakage protection at that junction.
To reduce the number of separate components that must be installed, the diaphragm housing, the adapter housing, and the gasket sandwiched therebetween, are sometimes assembled to form a single component. Current methods for assembling the remote diaphragm assembly include the use of screws, clips, nuts and bolts, and other similar fastening devices. These kinds of fasteners can lead to increased manufacturing costs due to the increased complexity of the remote diaphragm assembly and the numerous components. Additionally, these methods for assembling the remote diaphragm assembly require the use of tools resulting in a time-consuming assembly process. As a result, shipping costs can be high because diaphragm assemblies utilizing these types of fasteners are typically shipped disassembled and require larger packaging. Further costs are realized when the gasket of the remote diaphragm assembly requires replacement or inspection, due to a time-consuming disassembly process. As a result, there exists a need for a remote diaphragm assembly that can be easily assembled and disassembled by hand.
A remote diaphragm assembly, for use in the process control industry, is disclosed which can be quickly assembled and disassembled by hand by press-fitting a diaphragm housing and an adapter housing together. The diaphragm housing includes a flexible diaphragm and a first retention ring receiving portion. The adapter housing is configured to place the flexible diaphragm in fluid communication with a process fluid in a vessel and includes a second retention ring receiving portion. The first and second retention ring receiving portions align to form a retention ring cavity. A retention ring is positioned within the retention ring cavity such that portions of the retention ring occupy the first and second retention ring receiving portions to couple the diaphragm housing to the adapter housing. Also disclosed is a method for assembling the above-described remote diaphragm assembly. The method includes securing a retention ring to either the first or the second retention ring receiving portions and press fitting the diaphragm housing and the adapter housing together to couple the diaphragm housing to the adapter housing.